In recent years, conversion of the protocol of a mobile communication network into an IP (Internet Protocol) is studied extensively.
An IETF (Internet Engineering Task Force) recommends standardization of Mobile IPv6 specifications. (Refer to non-patent documents 1: Mobility Support in IPv6<draft-ietf-mobile-ipv6-24.txt>, Work in Progress).
Network configuration elements of Mobile IPv6 include an MN (Mobile Node), an HA (Home Agent) and a CN (Correspondent Node).
An MN has a unique IP address (or home address), which does not change even if the MN moves to another location. A link that has the same prefix as the home address is referred to as a home link. In this case, the prefix of an IP address is a network part of the IP address.
When an MN moves to a link other than the home link, in the other link where the MN presently exists, the MN acquires an IP address. This acquired IP address is referred to as a care of address, which is abbreviated hereafter to simply a CoA. When the MN moves to the foreign link defined as a link to which the MN has moved from the home link, the MN receives a router advertisement transmitted periodically by a router existing in the present network. As the MN detects a prefix included in the router advertisement as a prefix different from that of the home address, the MN becomes aware of the fact that the MN has moved from the home link to the foreign link. A message in the router advertisement is prescribed in a neighbor discovery (IETF RFC2461) of the IPv6 specifications. The message is used for informing another node in the same link as the router that the router exists in the same link.
When the MN detects its movement, the MN registers its CoA in the HA. The security of a binding update message and binding acknowledgement message is assured by using IPsec. The HA holds binding information in a binding cache. The binding information is information associating the home address of the MN existing in a foreign link other than the home link with the aforementioned care of address (CoA). Then, operating as a proxy of the MN, the HA multicasts a Gratuitous Neighbor Advertisement in order to intercept a packet transmitted from a CN to the home address of the MN.
A procedure for transmitting a packet from a CN to the home address of an MN is described as follows.
The CN transmits a packet directed to the home address of the MN. The HA intercepts a packet directed to the home address of the MN. The HA searches the binding cache for a CoA associated with the home address of the MN. Then, the HA adds an IP header directed to the CoA to the received packet in an encapsulation process and transmits the encapsulated packet to the CoA. The encapsulated-packet route between the HA and the MN is referred to as a mobile tunnel.
When the MN receives the packet directed to the CoA, the MN removes the IP header added earlier to the packet in a decapsulation process to restore the original packet. Security of the mobile tunnel can be assured by using IPsec. The MN receiving the encapsulated packet may inform the CN of the binding information in order to optimize the route from the CN to the MN.
As a technology for managing local movements based on the Mobile IPv6 specifications, Hierarchical Mobile IPv6 mobility management (HMIPv6) has been proposed. (Refer to non-patent documents 2: Hierarchical Mobile IPv6 mobility management (HMIPv6)<draft-ietf-mobileip-hmipv6-07.txt>, Work in Progress).
HMIPv6 is provided with a MAP (Mobile Anchor Point) between the HA and the MN. The MAP provides a local HA function. The MAP may also have an AR (Access Router) as a subordinate. The MN receives a router advertisement including MAP options from an AR or the MAP and acquires the IP address of the MAP. The MAP options include the global address of the MAP, the prefix of the MAP, a MAP preference and the number of hops along the route to the MAP. The MAP informs the AR of MAP options by adoption of one of the following methods:
(1) Deliver a router advertisement including MAP options to the AR (Access Router).
(2) Have the MAP extend a router renumbering function of IPv6 to notify the AR of MAP options.
Instead of having the MAP inform the AR of MAP options, a person in charge of network management may set information of MAP options in the AR.
Receiving a router advertisement including MAP options, the AR passes on the router advertisement including MAP options to the MN located at a subordinate location.
Receiving the router advertisement including MAP options, the MN conforming to HMIPv6 stores the information of the MAP options. The MN conforming to HMIPv6 then generates an RCoA (Regional Core of Address) from the MAP prefix included in the MAP options and an index identifier of the MN. The MAP prefix is the prefix of a link in which the MAP exists. In addition, the MN conforming to HMIPv6 also generates an LCoA (On-link CoA) by using prefix information included in the router advertisement transmitted by the AR. The prefix information is the prefix of the AR. The LCoA corresponds to the CoA of Mobile IPv6.
First of all, the MN conforming to HMIPv6 registers its CoA in the MAP. The MAP is an element for managing information associating the RCoA of the MN with the LCoA. Then, the MN conforming to HMIPv6 registers its CoA in the HA. When the MN moves inside the MAP, the MN updates only information cataloged in the MAP as information on the CoA of the MN.
In addition, attention is being paid gradually to a network mobility technology for managing mobility in network units by using a mobile router for supporting group movements of nodes. (Refer to non-patent documents 3: Network Mobility Support Goals and Requirements”<draft-ietf-nemo-requirements-01.txt>, Work in Progress). The mobile router has an HA and registers its CoA in the HA. The mobile router is provided with an MN function of the mobile IP and router function. In order to sustain session continuity while the mobile router is moving, a mobile IP technology is applied between the HA of the mobile router and the mobile router itself. The HA intercepts a packet directed to a terminal located at a location subordinate to the mobile router and transfers the packet to the mobile router. Thus, it is possible to sustain the session continuity while the mobile router is moving. An IP header is added to a packet transferred between the HA and the mobile router. A mobile network including a mobile router includes stationary nodes and mobile nodes. A mobile network may include another mobile network. When a node of a mobile network communicates with a node outside the mobile network, all traffics pass through a tunnel between the mobile router and the HA.
A virtual machine exists in a technology for emulating a specific machine architecture and a hardware platform. In general, the virtual machine is implemented by software. Normally, the virtual machine operates on an OS (Operating System) of an apparatus. For this reason, an OS used for executing the virtual machine itself is referred to as a host OS and an OS executed in the virtual machine is referred to a guest OS.
On the other hand, attention is paid to an SIP (Session Initiation Protocol) adopted as a session control protocol in an IP network. For more information on the SIP, refer to non-patent document 4: IETF RFC3261, SIP: Session Initiation Protocol. The SIP is a protocol for controlling sessions of IP multimedia communications made to conform to specifications by IETF. Representative services each adopting the SIP include a VoIP (Voice over IP) service. The VoIP (Voice over IP) service is a service adopting a technology for transmitting and receiving audio information by way of an IP network. In a VoIP communication adopting the SIP, a virtual session is set prior to the start of the communication between apparatus communicating with each other. Then, audio data put in an IP packet is transmitted through the set session. The SIP adopted in the VoIP communication establishes, maintains and terminates a session between the apparatus communicating with each other.
In addition, attention is paid to a TLS (Transport Layer Security) protocol adopted as a protocol for providing a security function on a session layer. For more information on the TLS protocol, refer to non-patent document 5: IETF RFC2246, The TLS Protocol Version 1.0. The TLS protocol is a security protocol positioned between a transport layer and an application layer as a protocol for authentication and encryption.